1. Field of the Invention
The present invention relates to a fuel cell system including a fuel cell stack formed by stacking a plurality of fuel cells in a stacking direction and end plates provided at both ends of the fuel cell stack in the stacking direction. Each of the fuel cells generates electricity by electrochemical reactions of a fuel gas and an oxygen-containing gas.
2. Description of the Related Art
For example, a solid polymer electrolyte fuel cell employs an electrolyte membrane. The electrolyte membrane is a polymer ion exchange membrane. In the fuel cell, the electrolyte membrane is interposed between an anode and a cathode to form a membrane electrode assembly (MEA). The membrane electrode assembly is sandwiched between a pair separators to form a power generation cell. In use, in the fuel cell, generally, a predetermined number of power generation cells are stacked together to form a fuel cell stack, e.g., mounted in a vehicle.
In the case where the fuel cell stack is used, in particular, in a vehicle as an in-vehicle fuel cell stack, it is desired to provide components such as fuel gas (e.g., hydrogen gas) system devices and oxygen-containing gas (e.g., air) system devices in a small space efficiently. In this case, it is necessary to protect the fuel gas system device preferentially against possible collisions of the vehicle.
For this purpose, for example, piping structure of a fuel cell disclosed in Japanese Patent No. 3671864 is known. In the piping structure, the stack is placed in a casing to mount the fuel cell stack in a vehicle. In the casing, fuel gas pipes, oxygen-containing gas pipes, and coolant pipes connected to the stack are provided. In comparison with the oxygen-containing gas pipes and the coolant pipes, inlet side fuel gas pipe and outlet side fuel gas pipes as the fuel gas pipes are provided closely to the stack, at positions closest to the stack in the stacking direction of cells.
In the piping structure, coolant pipes for supplying a coolant into or discharging the coolant from a coolant manifold in the fuel cell stack, and gas pipes for supplying reactant gases into or discharging the reactant gases from gas manifolds in the fuel cell stack are connected to an end plate provided at one end of the fuel cell stack. The gas pipes include fuel gas pipes for supplying a fuel gas into or discharging the fuel gas from a fuel gas manifold in the fuel cell stack, and oxygen-containing gas pipes for supplying an oxygen-containing gas into or discharging the oxygen-containing gas from an oxygen-containing gas manifold in the fuel cell stack. Further, among the fuel gas pipes, the oxygen-containing gas pipes, and the coolant pipes, the fuel gas pipes are provided at the innermost positions of the vehicle.